Addison G. Wright, "The Riddle of the Sphinx: The Structure of the Book of Qoheleth," Catholic Biblical Quarterly 30 (1968): 313-334. Reprinted in: Addison G. Wright, "The Riddle of the Sphinx: The Structure of the Book of Qoheleth," Roy B. Zuck,ed., Reflecting with Solomon: Selected Studies on the Book of Ecclesiastes. Grand Rapids: Baker, 1994. pp.45-66.